The Mekong River in Southeast Asia is filled with possibilities when it comes to hydropower development, but a number of concerns can make building new hydro facilities there tricky and uncertain.

As it flows south through Southeast Asia, the Mekong River — steeped in history and rich in wildlife — represents the future of progress and security for many in the region

In terms of hydropower, it's one of the least-developed among the world's great rivers. Rapidly industrializing Southeast Asian nations are eager to tap into its power, and countries with few resources but ample water supply are all too happy to oblige.

Because of this, 15 projects are now in some state of development on this river in China, Myanmar, Laos, Thailand, Cambodia and Vietnam. Eight projects representing more than 10,000 MW of capacity are proposed for development in Laos alone.

But there is uncertainty surrounding hydro development on the river and the tributaries that feed it. Downstream nations fear hydro projects constructed upstream will choke off waters needed for irrigating farms. But more worry that new dams will have an adverse impact on the region's fish populations, of which there are many species but relatively little knowledge.

The Mekong River holds great promise in terms of energy, but also a lot of questions for those concerned about its biodiversity and the welfare of the people who depend on it for daily life. That calls for careful planning, says one industry expert.

"The full benefits of hydropower can only be achieved when hydropower is developed in a sustainable way, sharing its many benefits and meeting the need to avoid, mitigate or adequately compensate for adverse impacts on local communities and environments," says Richard Taylor, executive director of the International Hydropower Association. "Correctly conducted and responsibly implemented project impact assessments and related management plans play a significant role in ensuring that this is achieved."

Current Development

Hydro development in the Mekong River region has been active, and plans now being made are ambitious, according to figures provided by IHA. Below is a breakdown of development under way or planned in the six countries mentioned earlier.

In Vietnam, developers added nearly 2 GW of capacity last year and plan to increase total capacity to 17 GW by 2020.

Cambodia has projects representing 720 MW of capacity under construction and another 958 MW planned with 193 MW commissioned in 2011.

Thailand has been more active in signing power purchase agreements, tapping into its neighbors' resources to fill its growing power needs, Taylor says. But that doesn't mean the country is sitting still. Developers there are planning to add two units with a total capacity of 500 MW to the Lam Takhong pumped-storage facility by June 2017. Work is also progressing on the 12 MW Bang Lang renovation, which is expected to be completed in 2015.

China has been particularly active in its hydropower development, adding 12.25 GW in 2011 to reach a total of 230 GW, IHA reports. Significant growth is expected, as China hopes to reach 280 GW by 2015 with about 7 GW of this being newly deployed on the upper Mekong River.

Myanmar now has about 360 MW of hydropower capacity in the region, but there are plans for much more. Myanmar Electric Power Enterprise has identified about 200 potential sites for hydropower development that could bring another 38 GW of installed capacity.

One of the region's smallest and poorest nations, Laos, is also planning big. The country has been seen as wanting to be "the battery of Southeast Asia," generating and exporting power to its more industrialized, energy-hungry neighbors.

Laos opened the 1,070 MW Nam Thuen 2 project in 2011 and 120 MW Nam Ngum 5 in 2012. Another 1 GW of hydro projects is under construction, and many more are being planned or are in the feasibility stage, IHA reports. Two projects being developed on Laos' border with Thailand represent a capacity of 2,951 MW, and that combined with other proposed projects could grow Laos' hydropower capacity by more than 10 GW by 2018.

Investors have been keen to help fund Laotian hydropower, with the South Korean Economic Development Fund signing a tentative US$70 million financing deal for hydro development on the Mekong. But Laos is also a scene of conflict between developers and those opposing dam construction. The latest epicenter of that dispute is the proposed 1,260 MW Xayaburi project.

Dam Construction Challenges

At US$3.5 billion, Xayaburi is one of the bigger proposed projects for Laos. Plans were going forward to begin construction, but those came to a halt earlier this year over concerns about how the dam might affect the river's ecosystem.

Under pressure from a collection of water and environmental ministers from Cambodia, Laos, Thailand and Vietnam, the Laotian government suspended construction on this project so more studies could be done regarding how the dam might affect downstream water supplies and the river's fish populations. These issues are being assessed intensively by the Mekong River Commission.

Food security is one issue cited by Xayaburi's critics, as some fear the project might limit water supplies to downstream farmers who needs large quantities of water for rice crops. People living along the river also depend on its abundance of fish, as that is the most plentiful source of protein in the region, says John Ferguson, an expert in fish passage issues who has studied some of the challenges facing hydro developers on the Mekong River.

Projects such as 4,200 MW Xiaowan in China, commissioned in 2010, impound water from the Mekong and generate power for an energy-hungry nation.

Ferguson says it has taken decades for American dam owners to hone the art of fish passage along western waterways like the Columbia River, which is where he has spent much of his career working. Ferguson says the standard fish ladders and turbine designs used to help preserve fish populations in the USA's Pacific Northwest can help hydro developers in Southeast Asia, but there are several differences that make fish passage issues there much more complicated.

On the Columbia River in the USA, for example, fish passage experts study about a half-dozen species that migrate up and down the river at fairly regular times. By contrast, there are about 125 species of migratory fish that travel up and down the Mekong River at varying times, Ferguson says. And while biologists have been able to compile robust documentation on fish in the USA, very little is known about species in the Mekong River.

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